1. Field of the Invention
The present invention relates to a structure of a connection portion of an exhaust pipe, where the connection portion is connected to an exhaust port of an engine, typically, an engine for a motorcycle.
2. Background Art
An example of a connection portion of an exhaust pipe, where the connection portion is connected to an exhaust port of an engine is disclosed in Japanese Patent Utility Model Laid open No. Sho 61 8802 1.
The above described related art structure is configured such that a collar is fitted to the outer periphery of an end portion of the exhaust pipe, and the inner peripheral surface of the collar is fixed to the edge of an end portion of the exhaust pipe by welding; and the exhaust pipe is connected to the exhaust port via the collar by means of bolts.
The above described related art structure, however, has the following problems:
(1) Since the exhaust pipe is connected to an exhaust port via the collar by means of bolts, stress concentration may occur at a welding portion between the exhaust pipe and the collar, thereby reducing the strength of the connection portion;
(2) a clearance between the exhaust pipe and the collar may become larger due to looseness therebetween and the like, thereby causing gas leakage due to occurrence of cracks or the like; and
(3) the welding control for preventing a reduction in flow resistance of exhaust gas flowing in the exhaust pipe due to welding beads formed on welding between the exhaust pipe and the collar is complicated.
In view of the foregoing, the present invention has been made to solve these problems of the related art, and to improve the overall state of the art.
An object of the present invention is to provide a new structure of a connection portion of an exhaust pipe for an engine.
To achieve the above object, there is provided a connection portion of an exhaust pipe, where the connection portion is connectable to an exhaust port side of an engine, the connection portion includes an extension portion extending radially outwardly and integrally formed on an edge of an end portion of the exhaust pipe; and a collar fixed to an outer periphery of the end portion of said exhaust pipe by crimping, wherein the edge of an end portion of said collar is abutted against said extension portion. With this configuration, the exhaust pipe can be rigidly connected to the exhaust port without occurrence of stress concentration therebetween; a clearance between the exhaust pipe and the collar is made as small as possible; since there is no welding bead appeared in the related art structure of a connection portion of an exhaust pipe, the flow resistance of exhaust gas is not increased, and therefore, it is not required to perform mechanical treatment for reducing the flow resistance of exhaust gas; and since the welding means is not required, it is possible to significantly reduce the cost.
In addition, to achieve the above object, there is provided a connection portion of an exhaust pipe, where the connection portion is connectable to an exhaust port side of an engine, the connection portion includes a reinforcing outer pipe fixed on an outer periphery of an end portion of the exhaust pipe by crimping; and a collar fixed on an outer periphery of said outer pipe. With this configuration, the reinforcing outer pipe can be rigidly fixed to the exhaust pipe without welding, to significantly increase the strength of the connection portion of the exhaust pipe, and also a clearance between the exhaust pipe and the outer pipe is made as small as possible.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.